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Solar Minimum Coming Sooner Than Expected

Posted by timothy on from the just-in-time-for-solar-tea dept.

bigjocker writes "According to this NASA story: "Something strange happened on the sun last week: all the sunspots vanished. This is a sign, say forecasters, that solar minimum is coming sooner than expected.""

6 of 79 comments (clear)

  1. Relax by Charvak · · Score: 3, Informative

    It happens every 11 or so years. Nothing to panic

    1. Re:Relax by Aglassis · · Score: 5, Informative

      The current theory (at least how I get it) is that sunspots are related to the magnetic field of the Sun. We start by assuming that the magnetic field of the sun starts a cycle by resembling a bar magnet (where a magnetic field line goes directly from the geographic south pole to the geographic north pole without curving). Due to the faster rotation of the Sun at the equator than at the poles (observed), the magnetic field slowly becomes twisted around the Sun (in a helix). Any field lines that resist the twisting can unwind causing them to erupt from the surface forming a sunspot pair (one where it exited and one where it returned). It is theorized that the greater magnetic flux at these points causes a reduction in convective heat transfer to the surface resulting in a dimming of the light at these spots. Eventually due to the interaction of the erupted magnetic field lines with the non-erupted magnetic field lines, the sunspots are forced towards the poles. Once enough sunspots are at the poles and their fields are stronger than the non-erupted fields, the field of the sun can flip, anhililating all the sunspots and returning the Sun to a normal bar magnet orientation (except with the opposite polarity). This is observed to take about 11 years.

      It seems that if all the sunspots have disappeared, this should mean that the magnetic field has reversed early.

      --
      Suddenly, the hairy finger of a familiar monkey tapped me on the shoulder. It was time.--G. T.
  2. Expanded info by Goyuix · · Score: 5, Informative

    After a bit of googling and actually reading the articles (gasp!) - here is some info that I found rather interesting:

    The sun cycle is about 11 years. The length isn't fixed, it has varied between 9 and 14 years.

    The next minimum was expected in late 2006, so this is coming about a year early.

    Scientists don't understand the solar year, or what really causes it - so this could be a fluke or something else. So far it is just an interesting observation.

    The linked article is good, but the Wiki link needs some help. Any solar physicists out there that want to contribute?

    1. Re:Expanded info by CheshireCatCO · · Score: 4, Informative

      The tidal force on the Sun due to Jupiter should be down by around a factor of 100,000 from that of the Moon on the Earth, I figure. And it's difficult to see how tides would affect the field. They create a bulge, they shouldn't tangle up field lines. And there is no reason that I can figure that would explain why it's a 22-year cycle, rather than an 11-year. (We see a maxiumum is solar activity every 11 years, but the Sun's field returns to the same orientation (north or south) every 22 years.) So while I'd say you've got a good thought, it doesn't look like it would pan out.

      What seems to be happening is that the convection and rotation that generates the field also tangles it all up. Eventually, it's so messed up that it starts to reconnect and straighten itself out, getting simpler and weaker. And the cycle starts again, but in the opposite direction.

      Incidentally, Earth seems to do the same thing, just much more slowly. Look for "magnetic reversals" with Google.

    2. Re:Expanded info by CheshireCatCO · · Score: 3, Informative

      It's difficult to see how; the topology hasn't changed. If the bulge were really severe, I could imagine it altering the way convection works, but there's no way that it is.

      Oh, I should have noted that the Sun rotates ever 30 days or so. The buldge moves across the Sun on that timescale, so Jupiter's orbital period is nearly irrelevent. (There's a slight effect from eccentricity of the orbit, but Jupiter's orbit is pretty circular.)

  3. post is late by awarlaw · · Score: 5, Informative

    according to www.spaceweather.com

    "One week ago, the sun was utterly blank: no sunspots. Now there are several. The largest, sunspot 682, is twice as wide as Earth -- and growing. But it does not yet pose a theat for strong solar flares. Solar activity should remain low in the days ahead."

    Low but not quite gone.
    Also, this just means that sunspots are fewer and farther between; not gone completely.

    --
    TIME is the Aether...